The World Almanac is the best I've found- it includes many that are not considered worthy of a biographical dictionary. I also have an old one (1970s) because older "stars" are dropped to make room for some new one's 15 minutes of fame.
The New York Times Crossword Puzzle Dictionary would also be a nice present for him.
Cheating? Puzzle makers employ everything, from the OED to atlases to special dictionaries to Bartlett's Quotations to thesauruses to foreign language primers to ......!